Tag: slag inclusion

  • Stick Welding Excessive Slag Inclusion Causes

    Stick Welding Excessive Slag Inclusion Causes

    Excessive slag inclusion in stick welding usually comes from poor slag removal, incorrect rod angle, low amperage, improper travel speed, restarting over trapped slag, or poor joint preparation. Slag inclusions occur when nonmetallic flux residue becomes trapped inside the weld instead of floating to the surface. This weakens weld integrity, reduces fusion quality, and can cause weld rejection on structural or code work.

    Common Symptoms

    • Dark lines or pockets visible inside the weld.
    • Slag trapped between weld passes.
    • Incomplete fusion near the weld toes.
    • Weld cracking along slag pockets.
    • Rough bead appearance with uneven slag release.
    • Grinding reveals trapped glassy material inside the weld.

    Likely Causes

    • Incomplete slag removal: Previous pass slag must be fully chipped and brushed before rewelding.
    • Low amperage: Insufficient heat prevents slag from floating properly behind the puddle.
    • Incorrect rod angle: Excessive drag angle can push slag ahead of the weld puddle.
    • Travel speed too fast: Rapid movement traps slag before it can rise out of the puddle.
    • Poor restart technique: Restarting directly on slag-covered craters traps contamination immediately.
    • Improper joint prep: Tight joints or poor bevel geometry restrict slag escape.
    • Weaving too wide: Excessive weave width can cool the puddle unevenly and trap slag at the toes.

    Inspection Steps

    1. Inspect weld passes for trapped slag lines or uneven bead edges.
    2. Chip and wire brush aggressively between all passes.
    3. Verify amperage settings for the rod diameter being used.
    4. Inspect rod storage conditions and electrode condition.
    5. Check weld joint geometry for proper slag escape.
    6. Inspect restart areas for trapped crater slag.
    7. Review rod angle and travel speed during welding.

    Visual Wear Indicators

    • Slag trapped at weld toes.
    • Glassy pockets revealed during grinding.
    • Irregular slag peeling patterns.
    • Cold lap appearance near weld edges.
    • Dark inclusion lines inside multi-pass welds.

    Common Wrong-Part Mistakes

    • Using low-hydrogen rods that were improperly stored.
    • Running incorrect polarity for the electrode type.
    • Using oversized electrodes on tight joints.
    • Trying to bury slag inclusions under additional weld passes.

    Field Fix vs Proper Fix

    Field fix: Increase amperage slightly, reduce travel speed, and clean between passes more aggressively. Proper fix: Grind out slag inclusions completely, correct joint preparation, improve restart technique, and verify the welding procedure matches the electrode type and position.

    Related Failure Paths

    • Undercut
    • Lack of fusion
    • Porosity
    • Restart cracking
    • Cold lap

    Safety Notes

    Grinding and slag removal produce sharp debris and airborne particles. Use face shields, safety glasses, gloves, and proper ventilation during weld cleanup and inspection.

    Sources Checked

    • Lincoln consumables catalogs
    • Lincoln equipment references
    • Uploaded welding safety and consumable references

  • 7018 Rod Sticking During Restarts: Causes and Fixes

    7018 Rod Sticking During Restarts: Causes and Fixes

    When a 7018 rod sticks during restarts, the usual problem is not the rod alone. It is usually a combination of a cold restart, heavy crater slag, poor restart prep, arc length too short, low amperage, weak work lead contact, or damp low-hydrogen electrodes. A 7018 electrode needs a clean restart point and enough current to re-establish the arc without burying the rod tip into frozen slag or unmelted metal.

    Common Symptoms

    • Rod freezes to the crater as soon as the arc is struck.
    • Restart piles up instead of tying into the previous bead.
    • Slag traps at the restart toe or centerline.
    • Arc starts, flashes, then goes out.
    • Electrode end turns black or balls over after repeated sticking.

    Likely Causes

    • Amperage too low: 7018 is a low-hydrogen, iron-powder electrode with medium penetration. If the current is low, the restart area will not wet in quickly.
    • Restart not cleaned: 7018 slag must be chipped and brushed before welding over it. Even a thin glassy film can hold the rod off the base metal and create inclusion.
    • Arc length too tight: Dragging the rod hard into the crater can extinguish the arc and freeze the electrode.
    • Wrong polarity or weak output: Standard E7018 is commonly run AC or DCEP depending on rod and machine. Wrong polarity, undersized leads, poor clamp contact, or long extension cords can make restarts sluggish.
    • Moisture exposure: Low-hydrogen rods that have been left open too long may restart poorly and increase hydrogen cracking risk on critical work.

    Inspection Steps

    1. Chip the crater completely and wire brush until the restart point is metallic, not dull gray slag.
    2. Check the work clamp on clean steel, not paint, rust, mill scale, or a loose table slot.
    3. Verify rod diameter and amperage. A 1/8 in. 7018 commonly runs around the 90–140 amp range depending on brand, position, and joint.
    4. Confirm polarity required by the actual electrode container.
    5. Inspect the rod end. If flux is broken back unevenly, restrike on scrap or break the end clean before restarting.

    Restart Technique

    Start slightly ahead of the crater, establish the arc, then move back into the crater long enough to remelt the end of the previous bead. After the puddle wets into both sides, continue forward. Do not start directly in a slag pocket. Do not stab the rod into the crater. Keep a short but live arc and watch the puddle edge, not the arc flare.

    Field Fix vs Proper Fix

    Field fix: turn amperage up 5–10 amps, clean the crater harder, and restrike on scrap before the restart. Proper fix: correct polarity, clamp contact, rod storage, joint prep, and restart technique. On code work, grind defective restarts out instead of burying them.

    Safety Notes

    Stuck electrodes are live electrical faults. Do not twist a stuck rod loose with bare gloves or exposed skin near grounded work. Break the electrode free safely, inspect the holder, and replace damaged stubs. Use proper welding PPE and ventilation.

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